Diamond spot size converter for fiber edge coupling

Abstract

An optical coupler configured to couple light along a propagation direction is disclosed. The optical coupler includes a lower area. The lower area includes a waveguide including a first end, a second end, and an inversely tapered portion. The optical coupler includes an intermediary area arranged over, in a vertical direction, the lower area. The intermediary area includes two or more intermediary elements. The optical coupler includes an upper area arranged over the intermediary area. The upper area includes one or more upper elements.

We claim: 
     
         1 . An optical coupler configured to couple light along a propagation direction comprising:
 a lower area comprising:
 a waveguide comprising a first end, a second end, and an inversely tapered portion; and 
 undercuts coupled to the waveguide via an intervening insulating layer, the undercuts being spaced apart along the propagation direction, and at least one of the undercuts comprising a material characterized by a first refractive index and comprising a fill material; 
   an intermediary area arranged over, in a vertical direction, the lower area and comprising:   two or more intermediary elements; and   an upper area arranged over the intermediary area and comprising:
 one or more upper elements; 
 wherein:
 at a facet, the waveguide, the two or more intermediary elements, and the one or more upper elements are arranged in a diamond shape, with the two or more intermediary elements laterally wider than both the one or more upper elements and the waveguide; 
 
 the undercuts are positioned below the waveguide with the intervening insulating layer between the undercuts and the waveguide, the undercuts being separated by portions that support the waveguide, and the waveguide forms a bridge between the undercuts. 
   
     
     
         2 . The optical coupler of  claim 1 , wherein at least a portion of the two or more intermediary elements are located outside, in a lateral direction, the one or more upper elements and the waveguide. 
     
     
         3 . The optical coupler of  claim 1 , wherein the intermediary area further comprises two or more secondary intermediary elements arranged below the two or more intermediary elements and arranged over the waveguide. 
     
     
         4 . The optical coupler of  claim 3 , wherein the two or more secondary intermediary elements have at least one dimension that varies. 
     
     
         5 . The optical coupler of  claim 3 , wherein the two or more intermediary elements and the one or more upper elements extend past the first end of the waveguide along the propagation direction and the second end of the waveguide extends past the two or more intermediary elements and the one or more upper elements along the propagation direction. 
     
     
         6 . The optical coupler of  claim 3 , wherein the two or more intermediary elements comprise a varying pitch along the propagation direction in a first section of the optical coupler. 
     
     
         7 . The optical coupler of  claim 6 , wherein the first section is closer to an optical fiber side of the optical coupler than a second section of the optical coupler. 
     
     
         8 . The optical coupler of  claim 7 , wherein at least one intermediary element of the two or more intermediary elements comprises a varying width along the propagation direction in the second section of the optical coupler. 
     
     
         9 . The optical coupler of  claim 1 , wherein the waveguide, the two or more intermediary elements, and the one or more upper elements comprise silicon nitride material. 
     
     
         10 . The optical coupler of  claim 1 , wherein the lower area further comprises a lower cladding layer of one or more cladding layers, wherein the intermediary area further comprises an intermediary cladding layer of the one or more cladding layers, wherein the upper area further comprises an upper cladding layer of the one or more cladding layers. 
     
     
         11 . The optical coupler of  claim 10 , wherein one or more cladding layer refractive indexes of the one or more cladding layers are lower than one or more element refractive indexes of the two or more intermediary elements and the one or more upper elements. 
     
     
         12 . The optical coupler of  claim 10 , wherein the one or more cladding layers comprise silicon dioxide (SiO2) material. 
     
     
         13 . The optical coupler of  claim 1 , wherein the first refractive index matches a refractive index of the intervening insulating layer or the waveguide. 
     
     
         14 . An optical coupler configured to couple light along a propagation direction comprising:
 a lower area comprising:
 a waveguide comprising a first end, a second end, and a first and second inversely tapered portion, wherein the first inversely tapered portion at least one of (a) tapers more gradually than the second inversely tapered portion; (b) has at least one dimension varying from the second inversely tapered portion; or (c) is nearer at least one of the first end or facet than the second inversely tapered portion; and 
   undercuts coupled to the waveguide via an intervening insulating layer, the undercuts being spaced apart along the propagation direction, and at least one of the undercuts comprising a material characterized by a first refractive index and comprising a fill material;   an intermediary area arranged over, in a vertical direction, the lower area and comprising:
 two or more intermediary elements; and 
   an upper area arranged over the intermediary area and comprising:
 one or more upper elements; 
 wherein:
 at a facet, the waveguide, the two or more intermediary elements, and the one or more upper elements are arranged in a diamond shape, with the two or more intermediary elements laterally wider than both the one or more upper elements and the waveguide; 
 
 the undercuts are positioned below the waveguide with the intervening insulating layer between the undercuts and the waveguide, the undercuts being separated by portions that support the waveguide, and the waveguide forms a bridge between the undercuts. 
   
     
     
         15 . The optical coupler of  claim 14 , wherein the optical coupler is configured to convert to and from a mode-field diameter (MFD) of a single-mode optical fiber (SMF). 
     
     
         16 . The optical coupler of  claim 14 , wherein the optical coupler is configured to convert to and from a mode-field diameter (MFD), wherein the MFD is more than 8 microns and less than 11 microns. 
     
     
         17 . The optical coupler of  claim 14 , wherein the optical coupler further comprises an insulating layer below the lower area. 
     
     
         18 . The optical coupler of  claim 17 , wherein the insulating layer is a buried oxide (BOX) layer. 
     
     
         19 . The optical coupler of  claim 17 , wherein the optical coupler further comprises a substrate layer below the insulating layer. 
     
     
         20 . An optical coupler configured to couple light along a propagation direction comprising:
 a lower area comprising:   a waveguide comprising a first end, a second end, and an inversely tapered portion; and
 undercuts coupled to the waveguide via an intervening insulating layer, the undercuts being spaced apart along the propagation direction, and at least one of the undercuts comprising a material characterized by a first refractive index and comprising a fill material; 
   an intermediary area arranged over, in a vertical direction, the lower area and comprising:
 two or more intermediary elements; and 
   an upper area arranged over the intermediary area and comprising:
 one or more upper elements, 
   wherein the two or more intermediary elements comprise a varying pitch along the propagation direction in a first section of the optical coupler,   wherein the first section is closer to an optical fiber side of the optical coupler than a second section,   wherein at least one intermediary element of the two or more intermediary elements comprises a varying width along the propagation direction in a second section of the optical coupler;
 wherein:
 at a facet, the waveguide, the two or more intermediary elements, and the one or more upper elements are arranged in a diamond shape, with the two or more intermediary elements laterally wider than both the one or more upper elements and the waveguide; 
 
   the undercuts are positioned below the waveguide with the intervening insulating layer between the undercuts and the waveguide, the undercuts being separated by portions that support the waveguide, and the waveguide forms a bridge between the undercuts.